chmod - Change protection on file

Change r - read, w - write and x - execute access to u - user, g - group and o - others. Examples:-

chmod u+w file1

Give user write-access to file1.

chmod g+r file2

Give group read-access to file2.

chmod o-w file3 file 4

Withdraw write-access to file3 and file 4 from others.

chmod -x file5

Give everyone execute-access to file5.